A SIMPLE METHOD FOR THE DETECTION OF THE TRANSPORT PATHWAYS OF MACROMOLECULES ACROSS ARTERIAL ENDOTHELIUM

血清大分子通过血管内皮层通过血管内皮层和内皮间裂隙运输到间质，但这些结构的通透性性质尚不清楚，而腔泡运输的方式也存在争议。我们发展了一种优雅的方法，在固定后进行原位示踪剂灌流，并对电子显微镜进行随机常规切片。我们观察到通过内皮层的空泡和细胞间通道，除了动脉内皮细胞高尔基体区周围的小泡外，只有少数小泡在细胞质中游离。无偏形态计量学显示，5%的腔隙和15%的细胞间裂隙形成了跨内皮通道。在N-乙基马来酰亚胺处理的大鼠主动脉中，细胞间通道形成的频率是生理对照的6倍以上，腔隙密度降至生理对照水平的80%，而较大的凹陷数目增加。因此，我们认为腔泡通道而不是跨细胞作用在血管内皮细胞中提供了一种空泡-囊泡运输的机制，因为跨细胞作用涉及许多游离小泡，而灵活的通道系统在动脉内皮细胞中广泛地作为大分子运输途径发挥作用。

Serum macromolecules are transported through the vascular endothelial layer to the interstitium via the caveolae and interendothelial clefts, but nature of the permeability of these structures is unknown, and the manner of caveola-vesicle transport is controversial, We have developed an elegant method of detecting macromolecular channels using an in situ tracer perfusion after fixation and random conventional sectioning for electron microscopy. We observed the caveolar and intercellular channels through the endothelial layer, and only a few population of vesicles free in the cytoplasm except those around the Golgi area of the arterial endothelium. Using unbiased morphometry, 5% of the abluminal caveolae and 15% of the intercellular clefts formed transendothelial channels. In rat aortas treated with N-ethylmaleimide, intercellular channels formed de novo at a frequency more than six times that of the physiological controls ; the density of the abluminal caveolae was decreased to 80% of the physiological control level while the larger invaginations increased in the number. We therefore propose that caveolar channels rather than transcytosis provide a mechanism of caveola-vesicle transport in the endothelium, because transcytosis involves many free vesicles, and that a flexible channel system functions extensively as a macromolecular transport pathway in the arterial endothelium.